The application of small or minimal amounts of flowable media to a laminar substrate presents a major problem, if the application is to be completely uniform. On the one hand, it is required to apply exactly the same amount of the medium to each surface unit over the entire width of the web of material and, on the other hand, the contact pressure of the web of material on a support surface must be the same over the entire width of the web.
It is already known to use magnetic wipers for printing or coating of web of material, i.e. roller wipers which are magnetically pressed against the web of material. In these magnetic wipers, from the supply of the medium to be applied, a wedge of flowable substance is formed in front of the magnetic wiper, wherefrom the required amounts of substance are taken.
It is clear that it is not possible in this manner to apply evenly small or minimal amounts of an application medium on a flat substrate, It is also already known to provide a trough with an application roller at the lowest point of the magnetic roller. However, such a trough, located under the magnetic roller is difficult to access and to inspect.